We use a copper tubed evaporator that we sell for around $300. We do charge about 15 hours labor to remove and replace the evpaporator, five vacuum servos, retrofit and charge. The vacuum servos are probably one of the most common problems guaranteed to come to every car eventually. A coupe of them require dash removal and one is inside the case itself. We always replace them as they only take a little more time now and ensure proper airflow afterwards and into the furure.
One of the most subtle losses of duct temperature is when the recirculate door isn't held closed. It can cost 10degs of duct temp loss to have it fully open. The most common duct problem is the loss of center vents with the air going through the defrost vents. This causes poor cooling efficiency and often causes a severe fogging problem on the outside of the window (at least in humid Florida).
BTW thanks for the nice comments about my shop and people.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician